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Ocean currents are important in the study of marine debris. [15] [16] Plankton are dispersed by ocean currents. Upwellings and cold ocean water currents flowing from polar and sub-polar regions bring in nutrients that support plankton growth, which are crucial prey items for several key species in marine ecosystems. [17]
A geostrophic current may also be thought of as a rotating shallow water wave with a frequency of zero. The principle of geostrophy or geostrophic balance is useful to oceanographers because it allows them to infer ocean currents from measurements of the sea surface height (by combined satellite altimetry and gravimetry ) or from vertical ...
Earth's trade winds and Coriolis force cause the ocean currents in South Pacific Ocean to circulate counterclockwise. The currents act to isolate the center of the gyre from nutrient upwelling, and few nutrients are transported there by the wind (eolian processes) because there is relatively little land in the Southern Hemisphere to supply dust to the prevailing winds.
The circumpolar current is driven by the strong westerly winds in the latitudes of the Southern Ocean. The ACC (red circle near the middle of the image) in relation to the global thermohaline circulation. In latitudes where there are continents, winds blowing on light surface water can simply pile up light water against these continents.
Flotsam can be blown by the wind, or follow the flow of ocean currents, often ending up in the middle of oceanic gyres where currents are weakest. Within garbage patches, the waste is not compact, and although most of it is near the surface of the ocean, it can be found up to more than 30 metres (100 ft) deep in the water. [69]
Winds drive ocean currents in the upper 100 meters of the ocean's surface. However, ocean currents also flow thousands of meters below the surface. These deep-ocean currents are driven by differences in the water's density, which is controlled by temperature (thermo) and salinity (haline). This process is known as thermohaline circulation.
Those currents comprise half of the global thermohaline circulation that includes the flow of major ocean currents, the other half being the Southern Ocean overturning circulation. [2] The AMOC is composed of a northward flow of warm, more saline water in the Atlantic's upper layers and a southward, return flow of cold, salty, deep water.
This return flow, as shown by Stommel, [1] occurs in a meridional current, concentrated near the western boundary of an ocean basin. To balance the vorticity source induced by the wind stress forcing, Stommel introduced a linear frictional term in the Sverdrup equation, functioning as the vorticity sink.